| For a long time,China is one of the countries which are most seriously damaged by wind erosion in the world.Wind erosion mostly occurs in arid and semi-arid areas of northern China.These areas are rich in mineral resources,and the level of social and economic development was relatively backward.After long-term large-scale and super intensive development of mineral resources,coupled with scarce precipitation,low vegetation coverage and other natural conditions,they are vulnerable to wind erosion.In view of the frequent occurrence of wind erosion in arid and semi-arid areas and the harmfulness of heavy metal pollution in tailings,this paper takes a typical copper tailings reservoir in the central arid zone of Ningxia as the research object to analyze the characteristics of heavy metal content in tailings.Through the indoor wind tunnel simulation experiment,the surface condition of tailings is simulated,and the wind erosion characteristics of tailings soil in the study area are analyzed According to the formula of dust emission from storage yard in the technical guide for compilation of dust emission inventory issued in 014,and the empirical formula that the dust emission from tailings is proportional to the high power of wind speed obtained by predecessors,the dust emission from tailings and wind erosion dust emission from tailings are estimated.Based on the data of meteorological elements such as annual wind speed,wind frequency,etc.,and combined with wind tunnel test data,different calculation methods are carried out Based on the evaluation of wind erosion potential,the distribution of heavy metals in the downwind direction of tailings is analyzed,and whether there is wind erosion pollution is judged.Some suggestions on wind erosion prevention and control are put forward on the basis of wind erosion evaluation,so as to provide some reference for the follow-up mine wind erosion prevention,pollution control and land reclamation.The main conclusions are as follows:(1)Based on the analysis of physical and chemical properties,heavy metal content and occurrence forms of tailings,the results show that the pH of tailings is alkaline,the salt content is high,and the nutrient element content is very low,which is in the sixth grade of the nutrient classification standard of the second National Soil Census,and the mechanical composition of soil is mainly sand;The average contents of Hg,Ag,Cr,Ni,Cu,Zn,as,Cd and Pb were higher than the background values of soil heavy metal elements in Ningxia,while the average contents of Cu,as and Cd were higher than the background values and screening values,The average proportions of available forms of Cu,Cd and as were 73.68%,24.79%and 5.58%,respectively.Therefore,the pollution degree and ecological risk of Cu were the highest.(2)Through indoor wind tunnel experiments,the variation of wind erosion intensity of tailings with wind speed under different water content and crust coverage was simulated,and the wind sand flow structure of sand collector was studied.The results show that:? the wind erosion intensity increases with the increase of wind speed under both schemes.The curve fitting of wind erosion intensity and wind speed shows that the exponential function can better fit the change of wind erosion intensity with wind speed;in both schemes,the wind erosion intensity of the rearranged bed is greater than that of the accumulated erosion process;with the increase of water content and skin cover,the wind erosion intensity is higher than that of accumulated erosion process;with the increase of water content and skin cover,the wind erosion intensity is better fitted with the exponential function The erosion strength is decreasing,which indicates that increasing water content and skin cover can play a good wind prevention effect.? Through the height fitting and cumulative distribution of sediment transport under different water content and skin cover conditions of tailings soil,it is found that the surface sediment transport volume of tailings land increases with the increase of wind speed;the height of the wind sand flow jump is positively related to the wind speed,and the sand transport volume increases with the wind speed,it tends to move to the high level,and the jump height of the low wind speed is lower,because the sand particles are mainly distributed at a lower height,The decay rate of sand concentration is higher with the increase of height.(3)The calculation results of tailing dust emission and wind erosion dust emission show that:?during the mining period,the annual tailing dust emission ranges from 270.05 kg/a to 302.98 kg/a,and the tailing dust emission is mainly caused by the loading and unloading transportation process,accounting for 78.65%-97.21%of the total dust emission,which is mainly affected by the change of average wind speed;during the stoppage period,the annual tailing dust emission is mainly caused by the wind erosion The emission range is 2.67?73.46 kg,and the variation trend of wind erosion dust emission is consistent with the maximum wind speed.?The dust emission of tailings ranges from 11.64 g/s to 44.792 g/s.The average annual wind erosion dust emission is 19.37 g/s,and the coefficient of variation is 51.61%.The variation of wind erosion dust emission in recent 13 years is moderate.During the period of 2008-2020,the average wind speed is 2.9 m/s.most of the time,the tailing sand will not be disturbed by the environmental wind speed,and the tailing pond will not produce dust.The amount of wind erosion caused by tailings dust is mainly affected by the maximum wind speed.(4)The evaluation of wind erosion shows that:?under the same wind speed,with the increase of crust coverage,the higher the wind erosion protection rate is,the smaller the wind erosion potential is.When the crust coverage is 50%,the wind erosion protection rate of the two schemes is more than 59.01%,and the possibility of wind erosion is small.For the water content,although the wind erosion intensity increases with the increase of water content under the wind speed of 10m/s,the main loss is water evaporation,but the wind erosion potential is very small under the low wind speed.Under other wind speed conditions,with the increase of water content,the higher the wind erosion protection rate,the smaller the wind erosion potential.?Through the wind erosion assessment of wind erosion dust emission and dust emission,the results show that the wind erosion dust emission of tailings during mining period is mainly in the loading and unloading transportation process,and the feasibility of long-distance transportation of dust caused by this process is limited.According to the daily meteorological data of the study area in recent ten years,the wind erosion dust emission is related to the wind erosion dust amount and the maximum wind speed,and the wind erosion dust phenomenon will not occur in most of the time.In the process of wind erosion,with the passage of time,there are less and less particles for blowing,more and more non erodible particles,the emission of wind erosion dust tends to be stable,and the probability of wind erosion dust in the follow-up process gradually decreases.? Through the determination of heavy metal content of soil samples from different distances of tailing downwind,it is found that the content of Cu,as and Cd in tailing is significantly higher than that in surrounding soil,and there is no significant difference in other elements.As the associated elements,as and Cd did not show an increase in content. |
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